1. Field of the Invention
The present invention relates to a driving method for driving a display device, and in particularly, a driving method performed by using a data driver.
2. Description of the Prior Art
According to the prior art, each pixel coupled to each data line of a display device has a common voltage signal respectively for defining its polarity. For example, if a voltage level of a common voltage signal of a pixel is higher than a predetermined voltage level, a polarity of the pixel is positive; and if the voltage level of the common voltage signal of the pixel is lower than a predetermined voltage level, the polarity of the pixel is negative. In order to prevent unclear display caused by electric charge accumulation, a display panel should perform a polarity switching after finishing each frame period, that is to switch the polarity of each pixel and a data line coupled to the pixel from being positive to being negative or from being negative to being positive.
However, due to demand for higher resolution of display devices, the reserved charging/discharging time is no longer long enough for a data voltage level of a data line to be switched from an original voltage level to a target voltage level, and a long voltage level switching time leads to the power consumption being too high. Hence, how to reduce the charging/discharging time of a data voltage level and reduce the power consumption required by a data driver are problems to be solved.
FIG. 1 illustrates signal waveforms when performing charge sharing according to the prior art. In FIG. 1, a first data line voltage level VY1 and a second data line voltage level VY2 are voltage levels of two adjacent data lines respectively. When a common voltage signal POL does not change yet, the first data line voltage level VY1 is positive, and the second data line voltage level VY2 is negative. When the common voltage signal POL changes, for example, from a low voltage level to a high voltage level, this means that a polarity of a data line changes, and a frame period finishes for the display device to enter a next frame period, the first data line voltage level VY1 changes from positive to negative, and the second data line voltage level VY2 changes from negative to positive. When the common voltage signal POL is detected to switch, a control signal STB is enabled to be at a high voltage level (within a time interval t1 shown in FIG. 1), a switch is turned on accordingly so as to couple a first data line and a second data line to a charge share line for the first data line voltage level VY1 and the second data line voltage level VY2 to be pulled to a charge sharing voltage level. As shown in FIG. 1, the charge sharing voltage level HAVDD is half the power supply voltage. The first data line voltage level VY1 and the second data line voltage level VY2 are then pulled to two target voltage levels, i.e. the first data line target voltage level Vtarget-Y1 and the second data line target voltage level Vtarget-Y2, respectively, according to the data inputted to the data lines. Performing the described charge sharing in the interval of the switching of polarity may shorten the required time for the first data line voltage level VY1 and the second data line voltage level VY2 to be pulled to the first data line target voltage level Vtarget-Y1 and the second data line target voltage level Vtarget-Y2 respectively so as to reduce the power consumption. According to prior art, the charge sharing is merely performed when the polarity of the pixels and the data line coupled to the pixels changes. However, taking the time interval t2 and the time interval t3 for example, the polarity of the data line does not change in the time intervals t2 and t3 so that the charge sharing is not performed for reducing the power consumption. In particularly, if the change of the first data line voltage level VY1 or the second data line voltage level VY2 is larger, more time is necessary for pulling them to the target voltage levels, and power consumption is therefore greater.